Glass fibers are typically treated after forming with a sizing composition that can impart desired properties. As used herein the term “size”, “sized”, “sizing” and “sizing composition” means a coating composition that can be applied to the glass fibers after formation of the fibers. After their formation and treatment, the sized glass fibers can be gathered into bundles or strands comprising a plurality of individual fibers.
A sizing composition can serve several functions. A sizing composition, for example, can serve as a lubricant, protecting fibers from abrasion with one another. A sizing composition can also function to enhance compatibility of glass fibers with the thermoplastic resins they reinforce.
Many glass fiber reinforced thermoplastic resins are used in the automotive industry. Glass fiber reinforced polyamide resins, for example, are often used to fabricate containers for various automotive fluids such as oil pans and radiator parts that encapsulate the core of the radiator. In recent years, manufacturing techniques have been developed to produce thermoplastic resins reinforced with long glass fibers. Processes such as G-LFT (Granular-Long Fiber Technology) and D-LFT (Direct-Long Fiber Technology) reinforce thermoplastic resins with fibers that maintain a sufficient length resulting in products with desirable mechanical properties and durability. Reinforcing thermoplastics with long glass fibers, however, presents several challenges including maintaining glass filament length and certain integrity during compounding or pultrusion processes while achieving sufficient wetting of the long fibers with thermoplastic resin, and others.
Moreover, once a long fiber thermoplastic (LFT) composite has been produced, certain end uses of the composite can involve exposure to harsh physical and chemical conditions that can lead to degradation of the composite through various pathways. The combination of high temperatures and exposure to aqueous organic solvent mixtures such as ethylene glycol and water, for example, can decrease the strength of some fiber reinforced polyamide resins.